1. Field of the Invention
This invention relates to improvements in air conditioning systems. More particularly, it relates to a thermal purge system that removes non-condensibles from a refrigerant fluid without discharging CFCs into the atmosphere.
2. Description of the Prior Art
In air conditioning systems, a refrigerant is alternately expanded into a gaseous state and condensed into a liquid state; heat is absorbed and released, respectively, as a result of such expansion and contraction. When the refrigerant is pure and unadulterated by contaminants such as air and moisture, the condensation is complete and the system operates at maximum efficiency; when contaminates enter the refrigerant, however, the condensation equipment is unable to condense all of such contaminates, and the efficiency of the system drops accordingly. In the industry, contaminants that cannot be condensed are known as "noncondensibles."
Noncondensibles enter most air conditioning systems because parts of such systems operate under a vacuum. Thus, those of ordinary skill in the art have attempted to build leak-proof systems, but a truly leak-proof system would be cost-prohibitive.
Most inventors, however, have accepted the fact of leakage and have developed systems designed to purge noncondensibles from the system. For example, U.S. Pat. No. 5,031,410 to Plzak, et. al., shows a refrigeration system thermal purge apparatus that adds a discrete purge refrigerant circuit to the conventional refrigerant circuit; the condensibles that are not condensed by the conventional condenser are exposed to the still lower temperatures of an auxiliary condensor. When the temperature within the auxiliary condensor drops to 18.degree. F., as detected by a thermostat, the contents of said auxiliary condensor are purged to the atmosphere. Although, at 18.degree. F., some separation of condensibles and noncondensibles will have been achieved, complete separation will not have been achieved; thus, some condensibles such as CFCs will be purged into the atmosphere. Moreover, thermostats are relatively unreliable within a five degree range; thus, purging may occur when the temperature within the auxiliary condensor is as high as 23.degree. F., and even less separation will have occurred at that temperature.
Thus, there is a need to provide a purge apparatus that provides a complete separation of condensibles and noncondensibles before the noncondensibles are purged to the atmosphere.
Moreover, the thermal purge units heretofore known are inefficient to the extent that they perform an extra condensation step, over and above the conventional step, but do not hold the condensible/noncondensible mixture at a low temperature for extended periods of time. Thus, insufficient time is available for the condensibles and noncondensibles to separate. The known systems also operate best under low load conditions, i.e., they are inefficient at high temperature gradients, because they lack means for metering additional liquid refrigerant into the auxiliary system as the load on the system increases.
There is a need, therefore, for a system that does more than merely provide an auxiliary condensation system that does not produce a complete separation of condensibles and noncondensibles.
When the prior art was considered as a whole, at the time the present invention was made, it neither taught nor suggested to those of ordinary skill in this field how an improved system could be built.